A study published in Science by behavioural ecologist John Hoogland of the University of Maryland says for most animals, individuals leave a territory to avoid competition with nearby relatives, such as mother or sibling. For three species of prairie dogs, however, individuals are more likely to disperse in the absence of nearby close kin.
Hoogland has been studying the ecology and social behaviour of prairie dogs in national parks in Arizona, South Dakota, and Utah for the last 40 years.
“The key to our research is that we live with the prairie dogs for five months of every year,” Hoogland said in a university release. “Students and I climb into our observation towers at the study colony at dawn each morning before the prairie dogs wake up, and we stay there until the last individual has submerged into its burrow for the night.”
The prairie dogs all have numbered ear tags and the flank of each individual is uniquely marked with fur dye so that it can be identified from a distance.
Hoogland said prairie dogs resemble other animals in competing with nearby kin for resources such as burrows and mates. But prairie dogs also co-operate with kin in the excavation of burrows that can be as deep as 15 feet; in defence of the home territory against prairie dogs from other territories; by giving alarm calls when a large predator attacks; and by helping to chase small predators such as long-tailed weasels. Another important co-operative behaviour is communal nursing, which can be life-saving for the unweaned offspring of close kin when the mother of those offspring dies for any reason.
According to the release, Hoogland hypothesizes that the benefits of co-operation with close kin exceed the costs of competition with those same close kin. When all close kin disappear, individuals disperse because they have nobody with whom to co-operate.